In newborn rabbits, small and apparently arbitrary regions of the olfactory bulb and associated epithelium appear capable of a high degree of odor processing. After medial or lateral removal of up to 80% of the olfact...
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In newborn rabbits, small and apparently arbitrary regions of the olfactory bulb and associated epithelium appear capable of a high degree of odor processing. After medial or lateral removal of up to 80% of the olfactory bulbs, including the accessory bulb, newborn pups were still able to respond appropriately to the pheromone-governing suckling behavior (Expt. I), could rapidly learn to associate a novel, artificial odor with suckling (Expt. II), and continued to respond appropriately to artificial odors learned prior to lesioning (Expt. III). These findings suggest that the perception and recognition of such suckling signals does not depend on the integration of information from the entire bulb or epithelium, and question the extent to which patterns of 2-deoxyglucose uptake in the bulb reflect the neural coding for specific odors. However, as the tasks set here only required detection of odor signals and not true odor discrimination, it may still be that the full bulbar pattern of activation is necessary for higher-order processing, such as distinguishing between odors and attributing different meanings to them.
Electrical microstimulation of the olfactory bulb in different locations has been shown to provide water-deprived rats with discriminative cues for selecting a palatable solution without tasting it in a two-choice tes...
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Electrical microstimulation of the olfactory bulb in different locations has been shown to provide water-deprived rats with discriminative cues for selecting a palatable solution without tasting it in a two-choice test. Some perceptive properties of bulbar electrical stimulation were investigated. It is shown that the perceptive effect evoked by stimulating a given site could be recognized when this site was stimulated together with several others. The animals'' perception of multi-site stimulation patterns seems therefore to be analytical rather than synthetic. Discrimination of stimulation patterns did not require presentation of concurrent patterns inside a short time interval. Identification of a multi-site pattern was possible when this pattern was presented alone in a test session. Individual characteristics of bulbar microstimulation appear to be perceived absolutely rather than differentially. A good retention of the discrimination learning of specific stimulation patterns was observed. Animals could identify stimulation patterns after complete interruption of the training for 17 days. The results are discussed with reference to the properties of the natural stimulation of the olfactory system.
An investigation was made into the ability of rats to discriminate between electrical stimulations applied to the mitral cell layer of the olfactory bulb in different locations. Water-deprived rats implanted with perm...
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An investigation was made into the ability of rats to discriminate between electrical stimulations applied to the mitral cell layer of the olfactory bulb in different locations. Water-deprived rats implanted with permanent electrodes were trained to use single- or multi-site microstimulations as discriminative stimuli for selecting a palatable solution without tasting it in a two-choice test. Spontaneous reactions of the animals to stimulation with sinusoidal currents higher than 3 .mu.A per electrode resembled sensory arousal. All rats were found to discriminate between the effects of concurrent microstimulations applied to bulbar sites separated by 500 .mu.m. Changing the current intensity in the range 4-20 .mu.A had no detectable effect on the discrimination. Discrimination was still possible, with a few exceptions, when electrodes were separated by 250 .mu.m and even when they were closely adjacent. spatial resolution of discrimination seemed not to vary in different regions along the rostrocaudal axis of the bulb. The discrimination of patterns of simultaneous stimulation at several sites was also investigated. Different multi-site patterns were easily distinguished, even when their respective components were closely adjacent or when some components occupied the same area. The findings are discussed with reference to the concept of spatial coding of odours in the olfactory bulb.
A linear model of information processing led to many experiments on learning difficulties in the subnormal and severely subnormal. It assumes learning can result from a break in the chain of information flow at any po...
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A linear model of information processing led to many experiments on learning difficulties in the subnormal and severely subnormal. It assumes learning can result from a break in the chain of information flow at any point but overlooks compensatory mechanisms common to a developing organism. To compensate for the model's difficulties, we compared blind and deaf children with subnormal and subnormal autistic children (i.e. localized with general cognitive incapacities). Absence of a modality led to alternative encoding strategies, but in certain circumstances they also occurred in the centrally handicapped. Reasons for the similarities and differences are discussed.
Two experiments are reported in which the presumed automatic nature of spatial coding is examined. In experiment 1, 48 young and 48 elderly female human adults, half of each group aware and half unaware of the task re...
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Two experiments are reported in which the presumed automatic nature of spatial coding is examined. In experiment 1, 48 young and 48 elderly female human adults, half of each group aware and half unaware of the task requirements, studied 16 cards with 4 nouns arranged vertically on each card. They were then given these 64 targets, as well as 64 distractors, and were required to sort the targets into 1 of 4 input spatial locations and to discard distractors. Awareness of the location requirement had no effect on performance and the 2 age groups were equivalent with respect to overall spatial memory accuracy. In a 2nd experiment, 40 young and 40 elderly unaware female adults were shown 64 cards with 1 noun per card in 1 of 4 spatial locations. There were no reliable age differences in location performance;the young adults, however, exhibited superior free recall.
The basic concepts necessary to understand the physical basis of NMR imaging are presented in this didactic article. It is intended as a starting point for the radiologist or medical physicist who is addressing the to...
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Visual receptive field properties of neurons in the region of the thalamic internal medullary lamina were studied in alert cats while they fixated in various directions. In slightly more than 50% of the cells, the res...
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Visual receptive field properties of neurons in the region of the thalamic internal medullary lamina were studied in alert cats while they fixated in various directions. In slightly more than 50% of the cells, the responsiveness of the cells depended on the location of the stimulus with respect to the head-body axis (stimulus absolute position). A cell could ignore a stimulus outside its absolute field even if it was well placed within its receptive field. Neurons distinguished were of 3 types. Neurons with small central receptive fields were tonically activated when the animal fixated the stimulus in 1/2 of the screen (usually contralateral). The firing rate of these cells was related to the stimulus absolute position measured along a preferred axis. Neurons with large receptive fields fired as a function of stimulus absolute position but stimulus fixation was not required. Neurons with eccentric fields responded to stimuli located in a target area defined in head-body coordinates. Such cells gave presaccadic bursts with eye movements terminating in the target area. Neurons apparently exist which code visual spatial information in a non-retinal frame of reference. This coding takes place at the time of stimulus presentation. Its role may be seen in the initiation of visually guided movements.
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